Power generation based on the combustion of biomass is regarded both sustainable and carbon neutral and is becoming an increasingly important source of energy.
A problem in biomass combustion is that the combustion products of the wide range of biomass fuels that are used are corrosive and may cause depositions on components in the biomass power plant. Especially exposed are superheaters, re-heaters and evaporators in biomass power plants, as well as in conventional steam boilers. A further problem in biomass power plants is that the materials in the components start to creep due to the high temperatures and the high pressures in the power plant. Today, biomass plants operate at a pressure of 150-200 bar and at a temperature of 500-550° C. In the future, biomass power plants temperatures are expected to be even higher than today, 600-650° C. This will put even higher demands on the hot corrosion resistance and the creep strength of the structural parts of the power plant.
Attempts have been made to increase corrosion resistance in steels. For example U.S. Pat. No. 4,876,065 and WO0190432 describe steels that are designed for use in corrosive environments in the oil- and gas industry.
Studies have further shown that austenitic stainless steel with high Mo content shows good resistance to high temperature corrosion: James R. Keisler, Oak ridge National laboratory, NACE Corrosion 2010, No 10081.
However, these steel do not exhibit the necessary creep strength to be suitable in biomass power plants.
Therefore, it is an object of the present invention to achieve an austenitic alloy which exhibits high corrosion resistance and high creep strength. It is also an object of the present invention to achieve a component for a steam boiler plant that comprises the inventive alloy.